drivers/watchdog/xen_wdt.c

   1 /*
   2  *      Xen Watchdog Driver
   3  *
   4  *      (c) Copyright 2010 Novell, Inc.
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #define DRV_NAME        "wdt"
  15 #define DRV_VERSION     "0.01"
  16
  17 #include <linux/bug.h>
  18 #include <linux/errno.h>
  19 #include <linux/fs.h>
  20 #include <linux/hrtimer.h>
  21 #include <linux/kernel.h>
  22 #include <linux/ktime.h>
  23 #include <linux/init.h>
  24 #include <linux/miscdevice.h>
  25 #include <linux/module.h>
  26 #include <linux/moduleparam.h>
  27 #include <linux/platform_device.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/uaccess.h>
  30 #include <linux/watchdog.h>
  31 #include <xen/xen.h>
  32 #include <asm/xen/hypercall.h>
  33 #include <xen/interface/sched.h>
  34
  35 static struct platform_device *platform_device;
  36 static DEFINE_SPINLOCK(wdt_lock);
  37 static struct sched_watchdog wdt;
  38 static __kernel_time_t wdt_expires;
  39 static bool is_active, expect_release;
  40
  41 #define WATCHDOG_TIMEOUT 60 /* in seconds */
  42 static unsigned int timeout = WATCHDOG_TIMEOUT;
  43 module_param(timeout, uint, S_IRUGO);
  44 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
  45         "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  46
  47 static bool nowayout = WATCHDOG_NOWAYOUT;
  48 module_param(nowayout, bool, S_IRUGO);
  49 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  50         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  51
  52 static inline __kernel_time_t set_timeout(void)
  53 {
  54         wdt.timeout = timeout;
  55         return ktime_to_timespec(ktime_get()).tv_sec + timeout;
  56 }
  57
  58 static int xen_wdt_start(void)
  59 {
  60         __kernel_time_t expires;
  61         int err;
  62
  63         spin_lock(&wdt_lock);
  64
  65         expires = set_timeout();
  66         if (!wdt.id)
  67                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  68         else
  69                 err = -EBUSY;
  70         if (err > 0) {
  71                 wdt.id = err;
  72                 wdt_expires = expires;
  73                 err = 0;
  74         } else
  75                 BUG_ON(!err);
  76
  77         spin_unlock(&wdt_lock);
  78
  79         return err;
  80 }
  81
  82 static int xen_wdt_stop(void)
  83 {
  84         int err = 0;
  85
  86         spin_lock(&wdt_lock);
  87
  88         wdt.timeout = 0;
  89         if (wdt.id)
  90                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
  91         if (!err)
  92                 wdt.id = 0;
  93
  94         spin_unlock(&wdt_lock);
  95
  96         return err;
  97 }
  98
  99 static int xen_wdt_kick(void)
 100 {
 101         __kernel_time_t expires;
 102         int err;
 103
 104         spin_lock(&wdt_lock);
 105
 106         expires = set_timeout();
 107         if (wdt.id)
 108                 err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
 109         else
 110                 err = -ENXIO;
 111         if (!err)
 112                 wdt_expires = expires;
 113
 114         spin_unlock(&wdt_lock);
 115
 116         return err;
 117 }
 118
 119 static int xen_wdt_open(struct inode *inode, struct file *file)
 120 {
 121         int err;
 122
 123         /* /dev/watchdog can only be opened once */
 124         if (xchg(&is_active, true))
 125                 return -EBUSY;
 126
 127         err = xen_wdt_start();
 128         if (err == -EBUSY)
 129                 err = xen_wdt_kick();
 130         return err ?: nonseekable_open(inode, file);
 131 }
 132
 133 static int xen_wdt_release(struct inode *inode, struct file *file)
 134 {
 135         int err = 0;
 136
 137         if (expect_release)
 138                 err = xen_wdt_stop();
 139         else {
 140                 pr_crit("unexpected close, not stopping watchdog!\n");
 141                 xen_wdt_kick();
 142         }
 143         is_active = err;
 144         expect_release = false;
 145         return err;
 146 }
 147
 148 static ssize_t xen_wdt_write(struct file *file, const char __user *data,
 149                              size_t len, loff_t *ppos)
 150 {
 151         /* See if we got the magic character 'V' and reload the timer */
 152         if (len) {
 153                 if (!nowayout) {
 154                         size_t i;
 155
 156                         /* in case it was set long ago */
 157                         expect_release = false;
 158
 159                         /* scan to see whether or not we got the magic
 160                            character */
 161                         for (i = 0; i != len; i++) {
 162                                 char c;
 163                                 if (get_user(c, data + i))
 164                                         return -EFAULT;
 165                                 if (c == 'V')
 166                                         expect_release = true;
 167                         }
 168                 }
 169
 170                 /* someone wrote to us, we should reload the timer */
 171                 xen_wdt_kick();
 172         }
 173         return len;
 174 }
 175
 176 static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
 177                           unsigned long arg)
 178 {
 179         int new_options, retval = -EINVAL;
 180         int new_timeout;
 181         int __user *argp = (void __user *)arg;
 182         static const struct watchdog_info ident = {
 183                 .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 184                 .firmware_version =     0,
 185                 .identity =             DRV_NAME,
 186         };
 187
 188         switch (cmd) {
 189         case WDIOC_GETSUPPORT:
 190                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 191
 192         case WDIOC_GETSTATUS:
 193         case WDIOC_GETBOOTSTATUS:
 194                 return put_user(0, argp);
 195
 196         case WDIOC_SETOPTIONS:
 197                 if (get_user(new_options, argp))
 198                         return -EFAULT;
 199
 200                 if (new_options & WDIOS_DISABLECARD)
 201                         retval = xen_wdt_stop();
 202                 if (new_options & WDIOS_ENABLECARD) {
 203                         retval = xen_wdt_start();
 204                         if (retval == -EBUSY)
 205                                 retval = xen_wdt_kick();
 206                 }
 207                 return retval;
 208
 209         case WDIOC_KEEPALIVE:
 210                 xen_wdt_kick();
 211                 return 0;
 212
 213         case WDIOC_SETTIMEOUT:
 214                 if (get_user(new_timeout, argp))
 215                         return -EFAULT;
 216                 if (!new_timeout)
 217                         return -EINVAL;
 218                 timeout = new_timeout;
 219                 xen_wdt_kick();
 220                 /* fall through */
 221         case WDIOC_GETTIMEOUT:
 222                 return put_user(timeout, argp);
 223
 224         case WDIOC_GETTIMELEFT:
 225                 retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
 226                 return put_user(retval, argp);
 227         }
 228
 229         return -ENOTTY;
 230 }
 231
 232 static const struct file_operations xen_wdt_fops = {
 233         .owner =                THIS_MODULE,
 234         .llseek =               no_llseek,
 235         .write =                xen_wdt_write,
 236         .unlocked_ioctl =       xen_wdt_ioctl,
 237         .open =                 xen_wdt_open,
 238         .release =              xen_wdt_release,
 239 };
 240
 241 static struct miscdevice xen_wdt_miscdev = {
 242         .minor =        WATCHDOG_MINOR,
 243         .name =         "watchdog",
 244         .fops =         &xen_wdt_fops,
 245 };
 246
 247 static int xen_wdt_probe(struct platform_device *dev)
 248 {
 249         struct sched_watchdog wd = { .id = ~0 };
 250         int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
 251
 252         switch (ret) {
 253         case -EINVAL:
 254                 if (!timeout) {
 255                         timeout = WATCHDOG_TIMEOUT;
 256                         pr_info("timeout value invalid, using %d\n", timeout);
 257                 }
 258
 259                 ret = misc_register(&xen_wdt_miscdev);
 260                 if (ret) {
 261                         pr_err("cannot register miscdev on minor=%d (%d)\n",
 262                                WATCHDOG_MINOR, ret);
 263                         break;
 264                 }
 265
 266                 pr_info("initialized (timeout=%ds, nowayout=%d)\n",
 267                         timeout, nowayout);
 268                 break;
 269
 270         case -ENOSYS:
 271                 pr_info("not supported\n");
 272                 ret = -ENODEV;
 273                 break;
 274
 275         default:
 276                 pr_info("bogus return value %d\n", ret);
 277                 break;
 278         }
 279
 280         return ret;
 281 }
 282
 283 static int xen_wdt_remove(struct platform_device *dev)
 284 {
 285         /* Stop the timer before we leave */
 286         if (!nowayout)
 287                 xen_wdt_stop();
 288
 289         misc_deregister(&xen_wdt_miscdev);
 290
 291         return 0;
 292 }
 293
 294 static void xen_wdt_shutdown(struct platform_device *dev)
 295 {
 296         xen_wdt_stop();
 297 }
 298
 299 static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
 300 {
 301         typeof(wdt.id) id = wdt.id;
 302         int rc = xen_wdt_stop();
 303
 304         wdt.id = id;
 305         return rc;
 306 }
 307
 308 static int xen_wdt_resume(struct platform_device *dev)
 309 {
 310         if (!wdt.id)
 311                 return 0;
 312         wdt.id = 0;
 313         return xen_wdt_start();
 314 }
 315
 316 static struct platform_driver xen_wdt_driver = {
 317         .probe          = xen_wdt_probe,
 318         .remove         = xen_wdt_remove,
 319         .shutdown       = xen_wdt_shutdown,
 320         .suspend        = xen_wdt_suspend,
 321         .resume         = xen_wdt_resume,
 322         .driver         = {
 323                 .owner  = THIS_MODULE,
 324                 .name   = DRV_NAME,
 325         },
 326 };
 327
 328 static int __init xen_wdt_init_module(void)
 329 {
 330         int err;
 331
 332         if (!xen_domain())
 333                 return -ENODEV;
 334
 335         pr_info("Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
 336
 337         err = platform_driver_register(&xen_wdt_driver);
 338         if (err)
 339                 return err;
 340
 341         platform_device = platform_device_register_simple(DRV_NAME,
 342                                                                   -1, NULL, 0);
 343         if (IS_ERR(platform_device)) {
 344                 err = PTR_ERR(platform_device);
 345                 platform_driver_unregister(&xen_wdt_driver);
 346         }
 347
 348         return err;
 349 }
 350
 351 static void __exit xen_wdt_cleanup_module(void)
 352 {
 353         platform_device_unregister(platform_device);
 354         platform_driver_unregister(&xen_wdt_driver);
 355         pr_info("module unloaded\n");
 356 }
 357
 358 module_init(xen_wdt_init_module);
 359 module_exit(xen_wdt_cleanup_module);
 360
 361 MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
 362 MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
 363 MODULE_VERSION(DRV_VERSION);
 364 MODULE_LICENSE("GPL");
 365 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);